Ian Poon's Blog

LTP is a key process underlying learning and memory. It involves the strengthening of synaptic connections through repeated stimulation, allowing neurons to communicate more effectively. This phenomenon is primarily mediated by NMDA (N-methyl-D-aspartate) glutamate receptors and other molecular mechanisms. Role of NMDA and AMPA Receptors Glutamate , the major excitatory neurotransmitter in the CNS, plays a critical role in synaptic transmission. It binds to two key receptors: AMPA Receptors : Ionotropic receptors that allow Na + and K + ions to pass when activated, leading to fast excitatory synaptic transmission . NMDA Receptors : Normally blocked by Mg 2+ ions, preventing ion flow. Definition: In this context, sensitivity refers to for the same amount of stimulation (AP to CA3), the response (AP of CA1) is greater. Phases of LTP A. Normal Synaptic Transmission (Before LTP) ...

The Photocascade Again, the membrane potential of a RPC is controlled by conductances of K + and Na + ions whose transmembrane gradients are maintained by pumps. In the dark, Na + ions flow into the photoreceptor through nonselective cation channels that are activated by the second messenger cGMP. Absorption of a photon triggers a biochemical cascade that lowers the concentration of cGMP, closing the gated channels and hyperpolarizing the cell to the K + potential.                            B: T refers to transducin(the G-protein for rods). For (C) notice cones are less sensitive than rods as mentioned Rhodopsin Activation Rhodopsin is the visual pigment in rod cells. Opsin component embedded in the disc membrane. Retinal is the light-absorbing moie...

Essentially BJT is just two neighboring pn junctions put back to back. BJT: a first pass (7.2) Fact In an IC npn transitor the emitter donor concentration \(N_{dE}\) is much greater than the base acceptor concentration \(N_{aB}\) which is much greater than the collector donor concentration \(N_{dC}\) \[ N_{dE}\gg N_{aB}\gg N_{dC} \] therefore the thermal equilibrium minority carrier concentrations in the emitter, base, and collector are \[ p_{nEo}=\frac{n^2_i}{N_{dE}}\ll n_{pBo}=\frac{n^2_i}{N_{aB}}\ll p_{nCo}=\frac{n_i^2}{N_{dC}} \] Forward-active regime: edge minority carrier concentration profile vs that of thermal equilibrium. Assume steady state short base diode conditions You should realize the heights of the thermal equilibrium minority carrier concentrations drawn in diagram above is a direct consequence of Fact 70 . This will again will be represented in the diagram Figure fluxpath where we account for flux paths of minority ca...

Now consider when voltage \( V_D \) is applied to the diode. Consider the forward biased case and observe the following figure the linear profile will be explained in the next section Recall from previously due to minority carrier injection into the QNR(outside the depletion region) \( n_p(-x_p)\gg n_{po}(-x_{po})=n_{po} \) \( p_n(x_n)\gg p_{no}(x_{no})=p_{no} \) This is essentially the concentration difference that drives the net diffusion into the QNR. See below for more Boundary Conditions Note that at the ohmic contacts in this figure we ensure that \( p_n(W_n)=p_{no} \) \( n_p(-W_p)=n_{po} \) that is the minority carrier concentrations are at their thermal equilibrium concentrations. Essentially we are saying that all excess carries injected starting from the edge of SCR must all recombine at the ohmic contact after diffusing across the negative concentration gradient assuming the balance between the very large ...

The pn Diode Circuit Symbol and Terminal Characteristics(6.1) There are 3 regions of operations of the pn diode Zero Bias- diode current \(I_D>0\) with the diode voltage \(V_D\approx 0.7 v\) Forward bias- diode current \(I_D\approx 0\) Backward Bias- diode current \(I_D<0\) and the diode voltage \(V_D< V_{BD}\) where \(V_{BD}\) is the diode’s breakdown voltage The transport of holes from the p side across the depletion region into the n side under a forward bias is called hole injection The transport of electrons from the n side to p side of the junction under a forward bias is called electron injection Let us see what is happening in the different regions Thermal equilibrium. Recap that the right side is the n side while the left is the p side. S-shape increasing graph will be the electrons while the S-shape decreasing graph will be the holes. No net hole or electron current density. All these covered in the 1st section if you recall We have \[|J...

WOOHOO I finally found a free blogging software that supports MathJax!  Testing math equation rendering: \begin{equation} \frac{V_1kC_{A0}}{F_{A0}} = \int_0^{X_{A1}} \frac{dX_A}{1-X_A}=\frac{(100 \cdot L)(0.6 \cdot min^{-1})(5 \cdot mol \cdot L^{-1})}{100 \cdot mol \cdot min^{-1}} \end{equation} https://www.quora.com/How-can-you-write-math-equations-on-Blogger-or-Blogspot Thanks so much my fellow Quora user!